Why are your emails being returned?

So, you’ve sent an email to a client and it’s been sent back with a load of gobbledygook attached to it which you don’t understand.

A typical email rejection message:

Subject: Undelivered Mail Returned to Sender
This is the mail system at host your-host.co.uk.

I’m sorry to have to inform you that your message could not be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The mail system

<recipipient@your-client.com>: host their-smtp-inbound.com []
said: 550 spamcop.mimecast.org Blocked – see

Hmm? What to do? This kind of thing is very frustrating and usually means you are on an email blacklist for some reason.

Email blacklists are everywhere. There are so many of them there’s a good chance your mail server’s IP address is listed on one of them.

In this particular case it’s SpamCop’s blacklist which is causing the problem. They work at mail-server level which means your mail system IP address is on the SpamCop list and is getting blocked by a recipient who uses the list. That’s why not all your emails are getting rejected.

How to fix it

We’ll refer to how you fix a SpamCop Blocking List (SCBL) entry.

Start by following the link in the email report you received from SpamCop. This link provide details about the reported email and SpamCop’s procedures you’ll need to follow.

Typical email blacklist websites

Sent emails keep getting rejected
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